import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';

/* class Square extends React.Component {
    constructor(props) {
        super(props);
        this.state = {
            value: null,
        };
    }
    render() {
        return (
            <button 
            className="square" 
            onClick={() => this.props.onClick()}>
            {this.props.value}
            </button>
        );
    }
} */
// 把 Square 组件重写为一个函数组件
function Square(props) {
    return (
        <button 
        className="square" 
        onClick={props.onClick}>
            {props.value}
        </button>
    );
}

class Board extends React.Component {
    renderSquare(i) {
        return ( // 传递给square组件
            <Square 
                value={this.props.squares[i]}  /* squares接收game父组件传的值，再将value传给square */
                onClick={() => this.props.onClick(i)}  /* onClick接收game父组件传的值 */
            />
        )
    }
    render() {
        return (
        <div>
            <div className="board-row">
                {this.renderSquare(0)}
                {this.renderSquare(1)}
                {this.renderSquare(2)}
            </div>
            <div className="board-row">
                {this.renderSquare(3)}
                {this.renderSquare(4)}
                {this.renderSquare(5)}
            </div>
            <div className="board-row">
                {this.renderSquare(6)}
                {this.renderSquare(7)}
                {this.renderSquare(8)}
            </div>
        </div>
        );
    }
}

class Game extends React.Component {
    constructor(props) {
        super(props);
        this.state = {
          history: [{ // 初始化history数组，保存每一步九个盒子的状态
            squares: Array(9).fill(null),
          }],
          stepNumber: 0, // 步数
          xIsNext: true, // 下一个是否是X落子
        };
    }

    jumpTo(step) {
        this.setState({
            stepNumber: step,
            xIsNext: (step % 2) === 0,
        });
    }
    // 点击事件处理函数
    handleClick(i) {
        const history = this.state.history.slice(0, this.state.stepNumber + 1);
        const current = history[history.length - 1];
        const squares = current.squares.slice();
        if (calculateWinner(squares) || squares[i]) {
            return;
        }
        // 棋子每移动一步，xIsNext（布尔值）都会反转
        squares[i] = this.state.xIsNext ? 'X' : 'O';
        this.setState({ 
            history: history.concat([{ // 添加新的历史记录
                squares: squares,
            }]),
            stepNumber: history.length,
            xIsNext: !this.state.xIsNext, // 改变下一步执行角色
        });
    }

    render() {
        const history = this.state.history;
        const current = history[this.state.stepNumber]; // 当前步数
        const winner = calculateWinner(current.squares); // 根据传入的每一步数组的状态，判断当前九个格子是否产生胜者

        // 
        const moves = history.map((step, move) => {
            const desc = move ?
              'Go to move #' + move :
              'Go to game start';
            return (  // 渲染出历史查看点击按钮
              <li key={move}>
                <button onClick={() => this.jumpTo(move)}>{desc}</button>
              </li>
            );
        });

        let status; // 头部是否胜利状态显示
        if (winner) { // 产生胜者
            status = 'Winner: ' + winner;
        } else { // 下一步的player
            status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');
        }
        return ( // 模板显示
            <div className="game">
                <div className="game-board">
                <Board
                    squares={current.squares}
                    onClick={(i) => this.handleClick(i)}
                />
                </div>
                <div className="game-info">
                <div>{status}</div>
                <ol>{moves}</ol>  {/* moves是一个数组，保存历史记录 */}
                </div>
            </div>
        );
    }
}

// ========================================

ReactDOM.render(
    <Game />,
    document.getElementById('root')
);

function calculateWinner(squares) {
    const lines = [
      [0, 1, 2],
      [3, 4, 5],
      [6, 7, 8],
      [0, 3, 6],
      [1, 4, 7],
      [2, 5, 8],
      [0, 4, 8],
      [2, 4, 6],
    ];
    for (let i = 0; i < lines.length; i++) {
      const [a, b, c] = lines[i];
      if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
        return squares[a];
      }
    }
    return null;
}